1995 Volvo Penta 3.0GS MHUG Backfire Problem

[95Glastronman]

Hello...I have a 1995 Volvo Penta 3.0 on my Glastron 175ssv that is backfiring when I reach higher rpm (3000+). Starts fine (usually pump twice when cold), idles great, and can run at a low speeds with no problems. As soon as I hit 20mph or so and 3,000 rpm..the engine basically stutters or feels like its loosing power and I hear a backfire. I think it is coming from carb but I am not sure. I checked the plugs I changed this season, they are a little dark but look good. Checked the plug wires, they look good. Checked the timing, all is good. Checked the cap and rotor for wear or corrosion, cap and rotor looked good. I have not put a meter to the rotor or tried turning it yet as I have read to do.

Any ideas on what could be the issue? Any help is greatly appreciated.

Thanks!

 

[Bondo]

Ayuh,.... Welcome Aboard,.... It's probably goin' Lean at high rpms,...

Check the fuel filters for crud, water, or bad gas,....

 

[95Glastronman]

Thanks for your reply..I did change the fuel filter and cleaned the filter in the carb. No signs of water and I think the gas is good. Doesnt smell sour or anything.

 

[95Glastronman]

Ive been reading a lot about the accelerator pump possibly causing this..how do I know if its bad and can I take it off the bottom of carb without taking the carb off?

 

[95Glastronman]

changed plugs to hotter plugs and no luck..could a dirty flame arrestor cause this? It was pretty gummed up. Just took it off and washed with gasoline.

 

[Bondo]

changed plugs to hotter plugs and no luck..

Ayuh,.... Hotter plugs ain't the answer, it's the wrong direction,....

If it's goin' Lean, Detonation will set in, 'n burn holes through the pistons,....
Hotter plugs will hasten that event,....

A dirty flame arrester might cause a Rich condition, but never a Lean condition,...

If the carb is gettin' good gas at a good flow, the carb needs to be taken off, 'n rebuilt,....
Complete tear down, soak, blow-out, 'n rebuild,...

 

[95Glastronman]

Thanks for all your thoughts...another question. How do I know from looking tin front of the engine what spot is number #1 on my distributor cap. Again, an unmodified 1995 3.0gs. Firing order is 1342. I just want to make sure im wired properly.